In railway and marine cargo terminals which handle a mixture of cargo containers and piggyback trailers, the use of front and side loading carriers is found advantageous because of their considerable mobility and accessibility to containers or trailers in a great variety of positions and surroundings. The utilization of these expensive vehicles may be improved if they may be provided with suitable spreader equipment to stack and unstack containers in a very dense arrangement, i.e., in rows of stacked containers with the row side-by-side with substantially no spacing therebetween. In this situation, a carrier equipped with a conventional "top-lifting" spreader, i.e., one limited in use to handling cargo containers only, is satisfactory for shifting the containers from the stacks to the hauling vehicles or vice versa.
If use of the carrier is suddenly required for the handling of the piggyback trailer, the carrier must be re-equipped with a trailer-handling implement providing grappling arms. Grappler-spreaders which handle both containers and trailers have not been suitable for such alternate service because of the protrusion of the "far side" grappler arms beyond the horizontal periphery of the top lifting spreader. Expressed another way, the grappling arms of the grappler spreader on the side thereof away from the carrier project horizontally beyond a vertical projection of a container top and thus interfere with containers stacked at a higher level than the level at which the grappler spreader is operated. The use of such a grappler spreader requires that the rows of stacked containers must be spaced a substantial distance apart to prevent interference of the grappling arms with stacked containers even though the grappling arms are always to a horizontal operative position. This is an unacceptable mode of stacking as stacking space is at a premium in many container terminal yards.
It is an object of the present invention to provide the grappler spreaders of a type which have great flexibility in the handling of containers and piggy-back trailers under a great variety of terminal yard conditions whereby carrier equipment may be used without changes of alternate load-handling implements.
It is also an object to provide grappler spreaders which are suitable for handling substantially all lengths of commercially used cargo containers and piggyback trailers.
A further object is to provide an expandable grappler spreader of which the grappling arms thereof are accommodated within a vertical projection of an upward projection of the top periphery of the shortest container handled by the implement.
Another object is to provide a spreader in accordance with the foregoing objects providing a frame which may receive fork tines or other cantilever elements of a front end loaded or side loaded mobile carrier.